This invention relates generally to filters, and more particularly concerns a high-volume filter for industrial sludge and the like.
In metal plating and similar operations, large amounts of process water must be discharged to sewers. This water contains much dissolved metallic salts, colloidally suspended rust, dirt, and other corruption. Modern high-volume metal treating operations can develop waste water sludges containing many hundreds of tons of such material in just a short time. So much such material can be present in the water that the discharge takes the consistency of a thin mud.
Environmental protection rules now prohibit or severely restrict discharges of this type in many areas. It is therefore necessary to filter large amounts of process water inexpensively just prior to discharge. Unless very large holding tanks or basins can be installed, this water must be filtered and discharged at a comparatively rapid rate.
A number of filter-type devices have been suggested to handle this material. A brief description of one such device, called a Lancy sludge filter tank, is found at page 40 in a book entitled Upgrading Metal Finishing Facilities to Reduce Pollution, published by the U.S. Environmental Protection Agency in 1973. In general, this Lancy sludge filter tank includes a tank in which are disposed one or more vertically elongated sludge filter decant panels. A hose communicates with the filter decant panel interior and tank exterior. After water seeps through the filter decant panel, water collects in the panel bottom and is drawn off through the hose for pH neutralization and ultimate discharge to a sewer.
Use of the Lancy sludge filter tank and like devices have presented a number of problems to at least some users.
The filters are comparatively expensive in initial purchase price and in installation costs. The decant panels comprise relatively large, expensive sheets of a felt-like polypropylene material which are separated, in the panel interior, by an expensive honeycomb structure. The honeycomb structure and filter panels are mounted on relatively heavy frames.
In operation, it has been found that after a short period of use, the outer panel pores become so clogged with sludge material that filtering action and filtered water discharge slow to a mere trickle. To clean the filter, the clogging sludge must be manually scraped from the panels. While this scraping is going on, the entire filter system must be removed from use. Removing the filter from use requires that other plant operations be halted, or that the developing sludge material be stored in large holding basins. Extensive costs are thus incurred. In addition, the heavy Lancy panels are continuously supported from overhead superstructure. This superstructure is an additional item of initial cost.
It is accordingly the general object of the present invention to provide a more effective, efficient, and lower-cost sludge filter.
A more specific object is to provide a vertical walled panel filter system which can process large amounts of industrial sludge at a faster rate than has been possible with preceding systems.
Another object is to provide such a filter in which the filtered sludge does not easily clog the filter.
A further object is to provide a filter of the type described and which is easy to maintain. A correlated object is to provide such a filter in which the filter members can be replaced or repaired quickly, and at low cost.
Another object is to provide such a filter which can be cleaned in place in minimal time.
A still further object is to provide such a filter which can be manufactured and inexpensively and offered at an attractively low price.
Yet another object is to provide such a filter which is reliable and rugged in use, and which will provide the user with a long service life.